DL-Malic acid (CAS 6915-15-7): storage and disposal
DL-Malic acid is held as a white crystalline solid in school and college prep rooms and university labs. It causes skin irritation and serious eye irritation. The same compound is sold as a food ingredient, so a tub with a vague label is a common problem. The way a powder takes on damp is usually the first thing a holder notices, and the label decides how it is described.
- CAS number
- 6915-15-7
- Form
- Solid
- Storage class
- Acid
- Signal word
- Warning
- Usual EWC code
- 16 05 06*
Harmful or irritant
What to do this week
- Check the label is readable and write down the opened date if it is not already there.
- Check it is stored as acid stock and apart from the items listed under "Do not store with".
- If you no longer need it, add it to your disposal list so it goes on the next collection.
Safe storage in a school or lab
Skin and eye irritation decide where this tub goes: low down on an acid-resistant tray in a ventilated corrosive store, with the lid firmly on, so dust stays out of the air and off the shelf. Keep it away from alkalis and oxidisers, because acids and alkalis react with heat and spattering if they meet. A tub bought as a food ingredient should be kept apart from laboratory stock and labelled, since the same name appears on both. Date it on arrival. A part-used tub that has been left on a bench is more likely to be caked than one in the store.
How to tell it has deteriorated
Loose white crystals or powder is normal. Caking is the first sign to look for, because the solid can take up moisture from the air and set into lumps, especially in a tub that has been left with the lid loose. Beyond that, check for a perished or brittle cap, crust around the neck, a cracked tub, discolouration and a faded or missing label. A tub with no label is the usual problem, because plain white powder tells you nothing. Anything caked, unlabelled or undated should be left closed and put on the collection list.
How it must be disposed of
By specialist collection only. It never goes down the drain or into general waste. It is normally packed in a corrosive acid laboratory pack with compatible chemicals.
Specialist collection is the only way out for DL-malic acid, whatever the tub looks like. It must never go into a sink, drain, kitchen bin or skip, and it must not be dissolved, diluted or neutralised first. As an organic acid outside a lab pack it takes 16 05 08*. Record whether the tub holds loose powder or caked lumps, how much is left and whether the label is readable. A collector groups it with other organic acids and keeps it away from alkalis and oxidisers, so itemise those separately on your inventory. Spilt crystals around the tub are worth mentioning.
| EWC code, laboratory chemicals | 16 05 06* |
|---|---|
| Discarded organic chemical, not a laboratory pack | 16 05 08* |
| Hazardous waste | Yes |
The code depends on where the waste came from and what it is mixed with. Use the waste code finder to see why.
Do not store with
- FlammableOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
- AlkaliAcids and alkalis react with strong heat and spattering if they meet.
- OxidiserMany oxidisers release toxic gas or become unstable in contact with acid.
- ToxicToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
Named chemicals to keep apart
- AcetoneOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
- Ammonia solutionAcids and alkalis react with strong heat and spattering if they meet.
- Calcium hypochloriteMany oxidisers release toxic gas or become unstable in contact with acid.
- EthanolOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
- FormalinToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
- HexaneOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
- Hydrogen peroxideMany oxidisers release toxic gas or become unstable in contact with acid.
- Mercury(II) chlorideToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
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- MethanolOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
- Potassium hydroxideAcids and alkalis react with strong heat and spattering if they meet.
- Potassium nitrateMany oxidisers release toxic gas or become unstable in contact with acid.
- Potassium permanganateMany oxidisers release toxic gas or become unstable in contact with acid.
- Sodium cyanideToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
- Sodium hydroxideAcids and alkalis react with strong heat and spattering if they meet.
- TolueneOxidising acids can ignite flammable materials, and acid fumes attack containers and seals.
Common quantities we collect
Usually held as: solid.
Part-used bottles and full containers are both fine. Tell us the size and how many, and an estimate is enough for a first price.
Where it is commonly held
Hazard statements
- H315 Causes skin irritation.
- H319 Causes serious eye irritation.
Precautionary statements
- P264 Wash hands and exposed skin thoroughly after handling.
- P264+P265 Wash hands and exposed skin thoroughly after handling. Do not touch eyes.
- P280 Wear protective gloves, protective clothing, eye protection and face protection.
- P302+P352 IF ON SKIN: Wash with plenty of water.
- P305+P351+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
- P305+P354+P338 IF IN EYES: Immediately rinse with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
- P317 Get medical help.
- P321 Specific treatment (see supplemental first aid instruction on this label).
- P332+P317 If skin irritation occurs: Get medical help.
- P337+P317 If eye irritation persists: Get medical help.
- P362+P364 Take off contaminated clothing. And wash it before reuse.
Substance as classified, dilutions may differ.
Questions
Can a school throw out old malic acid with kitchen waste?
No. It causes skin irritation and serious eye irritation, and a tub from a prep room is chemical waste even though the same name is sold as a food ingredient. It goes by specialist collection.
Why has the powder in our tub set into lumps?
The solid can take up moisture from the air, especially if the lid has been left loose. Lumps do not change the hazards. Keep the lid on, do not break the cake up, and list the tub for collection if it is old or unlabelled.
Where should it be stored in a college prep room?
Low down on an acid-resistant tray in a ventilated corrosive store, away from alkalis and oxidisers, with a firm lid and a date on the label. Keep any food grade tubs separate from it.
